1. Field of Invention
This invention relates to electric switches in general and particularly to a lockable structure enclosing an electric switch.
2. Description of Prior Art
With the widespread and ever-increasing use of all types of electrical equipment, there has developed a need for an apparatus which can control the unauthorized use of this equipment. The need for this type of apparatus has developed as a result of the increasing interest in and emphasis on security and safety, as related to the operation of electrical equipment.
In the field of power tools which are used in the home and in schools, there is a need to restrict the use of these devices to authorized users and prevent use thereof by small children in the home or students who have not received the appropriate training. There is a similar need to limit the use of certain electrical equipment such as grinders, food processors, and slicers. Devices currently on the market such as outlet covers provide little safety because they can be easily figured out by curious youth.
In the home, it is often necessary to control the use of television receivers and video tape recorders by children. This need is related to a desire to limit the extent of television viewing by children and to restrict this use to programming which is considered appropriate.
In commercial offices, there is often a need to restrict the use of office copiers, typewriters, and other electrical equipment and to prevent the use of this equipment by unauthorized persons. This requirement often occurs when an office must remain open for purposes of cleaning or maintenance after the end of the normal business day when the authorized personnel are no longer present.
Another reason for the development of a means of limiting the operation of equipment to authorized users has been the widespread application of computers to every phase of commercial and industrial activity. This has resulted in a situation where an unauthorized user can, either unintentionally or intentionally as a result of malice, do a substantial amount of damage. This damage can result from both the entry into computer networks and the destruction or tampering with the equipment or data, as well as the obtaining of sensitive information stored in these files.
In addition, in laboratories where certain electrically operated sensitive test equipment is located, there is a similar need to restrict access to such equipment.
Some newer types of electrical equipment include a keylock feature in which a removable key is used to activate a switch which applies electrical power to the equipment. This feature meets the need for a means of limiting the operation of the equipment to authorized users. However, this feature is found only in relatively expensive types of equipment and relies on a key that could be easily lost or require the creation of a large number of copies to grant access to all authorized users. Retrofitting this feature on existing equipment is quite costly and in most cases extremely difficult or impossible. Thus, there is compelling need for a practical and economical means for controlling the use of electrical equipment.
Inventors have created several types of security devices to control access to electrical equipment. Their approaches to this problem are undesirable because they do not combine simplicity, ease of manufacture, and programmable, keyless operation in a single design. Simplicity of installation and operation as well as ease of manufacture are important if the manufacturer wants to sell a quality product to the widest range of users at the lowest possible price. Keyless operation is important because it removes the need to carry around a set of keys to run each piece of equipment the user requires access to and avoids the problems of searching for and eventually replacing lost keys. Lock programmability is important because it allows the user to personalize combinations to numbers that are easy to remember. It also provides the user the option to standardize combinations to a single number that can be applied to all the equipment the user operates. These characteristics help make the device more marketable to the general public and industry.
U.S. Pat. No. 2,629,029 to Raphael (1953) employs a keyless device but denies the user the ability to program the combination. This design also ignores available off-the-shelf components as well as opens the user to a potential shock should the power switch lack the proper insulation necessary to separate the switch from the lock to which it is directly connected. U.S. Pat. No. 3,774,049 to Coleman (1973), also a keyless device, focuses mainly on automobile applications. This design also relies on a pre-assigned combination and requires many custom components resulting in higher manufacturing costs.
U.S. Pat. Nos. 3,524,029 to Laff (1970), 4,063,110 to Glick (1977), 4,479,688 to Jennings (1984), 4,482,789 to McVey (1984), and 4,647,735 to Sicher (1987) require keys to engage the flow of electricity from the electrical wall outlet to the electrical connector receptacle. U.S. Pat. No. 5,061,199 to McClead (1991) requires a total of three keys to regulate its' operation, increasing the expense and complexity of implementing this electrical apparatus. This apparatus also requires electrical appliances to employ an electrical connector with holes in the blades to allow insertion of a locking rod. With this limitation, connector designs such as the pole type employed abroad are excluded from being used in this device. U.S. Pat. No. 3,247,337 to Wiegel (1963), an invention focusing on controlling the flow of electricity at the circuit breaker level, requires only a single key but does not provide a means to secure electrical appliances to a source of power. U.S. Pat. No. 3,524,029 to Laff (1970) includes a permanently fastened lid that denies the removal of the electrical connector from the device, preventing the user from removing or replacing the protected appliance. U.S. Pat. No. 5,193,665 to Jankow (1993) requires a key to engage the flow of electricity from the electrical wall outlet to the electrical appliance cord. This design additionally restricts the use of this device to a single appliance because it is directly part of the appliance cord. The last eight patents pose a potential safety risk because they lack the ability to stop the flow of electricity through the device without first inserting a key into the lock. This safety risk makes the devices undesirable for areas where children are present or where a "panic button" is required.